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The Draft Value Chart: Right or Wrong?

Posted by Chase Stuart on May 21, 2008

I'm sure most of the PFR readers have seen the NFL draft value chart, sometimes referred to as the Jimmy Johnson draft chart. Lots of people have discussed whether it's accurate, and whether it's still valuable in an era of escalating salaries. I'll sidestep the salaries issue today, and just focus on the actual draft value chart.

For one, how would we know whether or not it's accurate? I suppose there are a few ways of analyzing that, but you need to assign some basic value to each draft pick. We know that Pick N is always better than Pick N+5, but how big is that difference if N = 5, or N = 25, or N = 100?

I looked at every draft from 1970 to 1999, giving me thirty years of drafts. I then assigned the approximate career value of each player to his rookie draft slot. So for the number one pick, we've got 133 points of value from Peyton Manning, 77 points of value from Keyshawn Johnson, 32 points of value from Kenneth Sims, and the value from all the other number one picks from 1970 to 1999. If you do this for the first 224 picks in every draft, and you can then get an average value for each draft pick.

There are some bumps in the data, of course. The seventh pick in the draft has an average value of 39, and the eighth pick an average value of 51, over the thirty years. The 7th pick has a lot of busts (Reggie Rogers, Brian Jozwiak, Joe Profit and Andre Ware) and not that many stars (Phil Simms, Champ Bailey and Bryant Young are the best players). The 8th pick has Ronnie Lott, Willie Roaf, Leslie O'Neal, Otis Anderson and Mike Munchak, and fewer busts.

Since the approximate values of the players that correspond to the draft picks fall off exponentially, I used a logarithmic formula to best fit the data. The formula to predict any NFL draft pick's approximate value in the NFL is:

    Approximate Value = -12.583 * Ln(draft pick) + 73.195

You end up with a list that looks like this:


1	73

2	64

3	59

4	56

5	53

6	51

7	49

8	47

9	46

10	44

11	43

12	42

13	41

14	40

15	39

16	38

17	38

18	37

19	36

20	35

21	35

22	34

23	34

24	33

25	33

26	32

27	32

28	31

29	31

30	30

31	30

32	30

33	29

34	29

35	28

36	28

37	28

38	27

39	27

40	27

41	26

42	26

43	26

44	26

45	25

46	25

47	25

48	24

49	24

50	24

51	24

52	23

53	23

54	23

55	23

56	23

57	22

58	22

59	22

60	22

61	21

62	21

63	21

64	21

65	21

66	20

67	20

68	20

69	20

70	20

71	20

72	19

73	19

74	19

75	19

76	19

77	19

78	18

79	18

80	18

81	18

82	18

83	18

84	17

85	17

86	17

87	17

88	17

89	17

90	17

91	16

92	16

93	16

94	16

95	16

96	16

97	16

98	16

99	15

100	15

101	15

102	15

103	15

104	15

105	15

106	15

107	14

108	14

109	14

110	14

111	14

112	14

113	14

114	14

115	13

116	13

117	13

118	13

119	13

120	13

121	13

122	13

123	13

124	13

125	12

126	12

127	12

128	12

129	12

130	12

131	12

132	12

133	12

134	12

135	11

136	11

137	11

138	11

139	11

140	11

141	11

142	11

143	11

144	11

145	11

146	10

147	10

148	10

149	10

150	10

151	10

152	10

153	10

154	10

155	10

156	10

157	10

158	9

159	9

160	9

161	9

162	9

163	9

164	9

165	9

166	9

167	9

168	9

169	9

170	9

171	8

172	8

173	8

174	8

175	8

176	8

177	8

178	8

179	8

180	8

181	8

182	8

183	8

184	8

185	8

186	7

187	7

188	7

189	7

190	7

191	7

192	7

193	7

194	7

195	7

196	7

197	7

198	7

199	7

200	7

201	6

202	6

203	6

204	6

205	6

206	6

207	6

208	6

209	6

210	6

211	6

212	6

213	6

214	6

215	6

216	6

217	5

218	5

219	5

220	5

221	5

222	5

223	5

224	5

How does this compare to the NFL draft value chart? I plotted them both on the same graph, with the NFL chart in blue and my chart in red. Take a look.

Draft Charts

Both start out very high, and drop off pretty fast. However, from picks 4 to 100, the NFL draft chart is pretty perfect. Picks 1, 2 and 3 are very overvalued, in increasing order. After about pick 100, every pick is overvalued again, in increasing order. So pick 180 is pretty undervalued by NFL GMs, but pick 120 is just mildly undervalued.

Now if the really, really early picks are overvalued, and the last four rounds are overvalued, why did I call the picks in the middle set of picks perfectly valued? While they're obviously undervalued with respect to picks not in the four to ninety-five range, the drop-off rate is captured almost perfectly by NFL draft charts. So the Jimmy Johnson chart does an excellent job of capturing the marginal value of the difference between pick 8 and pick 37, or between pick 46 to pick 85. While the whole group of picks is undervalued, they're pretty much all undervalued by a similar amount.

Here's an example. According to the NFL draft value chart, picks 2, 161, 162 and 163 are worth 2,680 draft points. Similarly, picks 26, 27, 28 and 29 are worth 2,680 points. But according to my chart, the first set of selections is worth 91 points in approximate value, and the second set of picks is worth 126 points in value. That's pretty significant -- it's the difference between Emmitt Smith or Junior Seau, and Roger Craig or Greg Lloyd. The middle of the road #2 picks have been Kevin Hardy and Tony Casillas. At 161-163, you're looking at someone who's not likely to ever be a starter. Forty-two of the 90 players drafted at 161, 162 or 163 had zero approximate value points for their career; thirty-eight of them never played a down in the NFL. Picks 26 through 29 are a bit more valuable. Mark Ingram, R.W. McQuarters, William Floyd and Darion Conner might be your four picks at those spots.

I've been thinking about this for a bit, and I've come to the conclusion that my draft chart is correct... and so is the NFL one. How can that be? In short, they measure different things. My draft value chart is excellent at telling you the average production you can get from any draft spot. That's important to use when running a study that deals with the expectations of rookies.

But NFL teams aren't always concerned with what the average pick will yield. Why are the bottom draft picks overvalued? If a team's sixth round pick is terrible, as opposed to just pretty bad, that's not going to matter much to the team. He won't play very either way. There's some minimum baseline a player needs to reach in order to be able to play, and some late round picks will fall below that spot. But since NFL teams aren't really hurt by late round picks that are say, really awful, they can be a bit risky. But in my system, the 200th pick will get knocked down quite a bit if a guy stinks.

Suppose that all seventh round picks have a distribution that looks something like this: 30% of the time they're a 1 out of 10, 30% of the time they're a 2 out of 10, 30% of the time they're a 3 out of 10, and 10% of the time they become something like a 5 out of ten. On average, that means 7th round picks are a 2.3, and that's what the Chase draft value chart would say. But assume that NFL teams won't give playing time to a guy that's not a three out of ten. So for NFL team's purposes, 40% of the time they'll have this 7th round pick be a 3 or a 5, and the other 60% of the time they'll play some other guy at that position. The NFL team doesn't have to eat the costs of the ones or twos out of ten. When it comes to late round picks, high upside is a lot more important than average position. This is why the NFL pick value chart "overvalues" later round picks compared to my draft chart. I suspect every NFL GM would take a "6" and a "1" from two 7th round picks than two "four". But my system would tell you the two "fours" are more valuable. We need to keep in mind that the two charts simply measure things, and having different values assigned to different ratings is perfectly fine.

What about those first three picks? Well, sort of the same thing is going on there. As a general matters, I think teams shoot for upside. Most fans and GMs would prefer a chance to win the SB and a chance to not make the playoffs, over a guaranteed playoff team with little chance of winning it all. Upside risk is especially important when you're talking about the top picks, because those can be the guys that take you to the Super Bowl (Manning, Elway, Bradshaw, Pace, and Aikman, e.g.). Further, I think GMs probably have a bit of overconfidence when they're trading up for the top pick. If a team trades up to get the first or second pick in the draft, they probably don't think they'll end up with Russell Maryland or Tony Boselli; they think it's going to be O.J. Simpson or Peyton Manning. So even if they know the average #1 pick is worth X, they probably think they're going to get the next Hall of Famer. And they're willing to take some risk on the top picks, and "overpay" compared to how they'll perform on average, because to NFL GMs, variance matters. If you asked a GM would they rather get an "8" from the second pick in the draft, or a 50/50 shot at either a "10" or a "5"...I think most GMs would flip the coin. The 10 can be a franchise changing pick, and they'll take on added risk even if it's not a positive expected value play. Once again, this is why it's perfectly fine that the NFL draft chart "overvalues" the top picks relative to my chart.

This entry was posted on Wednesday, May 21st, 2008 at 5:37 am and is filed under Approximate Value, NFL Draft, Statgeekery. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.